1. Field of the Invention
This invention relates to an apparatus for needling a circular nonwoven web, which has preferably the configuration of s circular ring, comprising a needle board, which carries a multiplicity of needles and is adapted to be driven to reciprocate said needles in a piercing direction, and a turntable, which is operable to rotate about an axis of rotation and comprises a web support for supporting said nonwoven web in such a position that said needles are adapted to pierce said nonwoven web supported by said web support.
2. Background of the Invention
It is known (from EP-B1-0,232,059) that a nonwoven web comprising one or more plies and having the configuration of a circular ring can be needled in that the nonwoven web is moved on a turntable past needling means, which have a working width that is adapted to the width of the annular nonwoven web. Because the turntable in the region in which it is contacted by the annular nonwoven web constitutes a continuous support for the nonwoven web to be pierced and for that purpose is made, e.g., of a foamed plastic, it is possible to needle the nonwoven web also during a plurality of revolutions. But a disadvantage of such needling means resides in that the nonwoven web is not uniformly needled over its width because the nonwoven web is moved on a circular path and the needles are uniformly distributed over the needle board in the usual manner. In that connection it must be borne in mind that the circumferential velocity of the annular nonwoven web is higher near its outer radius than near its inner radius so that the piercing density will be lower in the outer portion of the annular nonwoven web than in its inner portion, i.e., the needling density will not be uniform over the width of the annular nonwoven web, if the needles are uniformly distributed over the surface of the needle board, which extends radially with respect to the axis of the turntable.